The present invention concerns a monophase electromechanical transducer whose stator has a planar structure and whose rotor includes one permanent magnet, in particular a bipolar magnet. In particular, the present invention concerns electromechanical transducers of small dimensions, in particular adapted to watch applications.
The man skilled in the art knows various electromechanical motors, in particular in the horological field, whose stator has a planar structure and whose rotor includes a permanent magnet. As regards monophase electromechanical motors, specialists in the field of horological electromechanics know the xe2x80x9cLavetxe2x80x9d type stepping motor. This motor includes a stator plate defining two magnetic stator poles of which two respective polar expansions define a stator hole within which is situated a bipolar permanent magnet mounted on the shaft of the rotor. The two magnetic stator poles define respectively two magnetic contact ears forming respectively two ends of the stator plate. A core carrying a coil and also having at its two ends two magnetic contact ears is fixed so that the two ears of the core are superposed onto the two respective ears of the stator plate. In a motor of this type, the core carrying the supply coil is always situated at the periphery of the stator plate. Swiss Patent No 639 525 shows in FIG. 1 a monophase stepping motor of the xe2x80x9cLavetxe2x80x9d type which has just been described. As can be seen in FIGS. 1 and 2 of this Patent Document, the stator plate defining the two magnetic stator poles may be used as a base plate for mounting at least partially various elements of the watch movement.
Swiss Patent No 648 984 discloses a timepiece including a monophase stepping motor of the xe2x80x9cLavetxe2x80x9d type described hereinbefore. This Patent Document discloses in particular the use of the stator of the monophase motor as base plate for the clockwork movement. Several mechanical and/or electronic elements are assembled on the stator plate used as the plate for the movement. In FIG. 1 of Swiss Patent No 648 984, the arrangement of core carrying the coil at the periphery of the clockwork movement has the drawback of limiting the arrangement of various elements on the plate, which constitutes a limiting restriction for the watch designer.
When the watch designer places a monophase xe2x80x9cLavetxe2x80x9d type motor in a movement in which the coil of the monophase motor is not situated at the periphery of the plate of the movement, the aforementioned stator plate forms a materially different part from the movement base plate as is seen in FIG. 1 of Swiss Patent No 643 704. In the design disclosed in Swiss Patent No 643 704, the stator of the monophase motor and the base plate of the clockwork movement form two materially distinct parts, which increases the manufacturing cost and limits the miniaturisation of the clockwork movement. The aforementioned problem of the resulting space requirement is further accentuated when the clockwork movement includes several monophase motors.
An object of the invention is to provide a monophase electromechanical transducer having a stator able to be used as a plate for the assembly of a device which is easy to make, inexpensive and leaves the designer complete freedom in arranging the device, in particular in positioning the rotor and the coil of this monophase transducer.
Another object of the invention is to provide an electromechanical device including a plurality of electromechanical transducers at least one of which is a monophase transducer which has the same features and advantages as that proposed in relation to the aforementioned first object.
Another object of the invention is to provide a device including a plurality of monophase transducers allowing compact and inexpensive design of the device.
The present invention therefore concerns a monophase electromechanical transducer, in particular of the horological type, including:
a stator made of magnetic material;
a rotor including a permanent magnet;
a coil;
said stator including a planar structure and a core around which said coil is mounted, said planar structure defining two magnetic stator poles whose two respective polar expansions define a hole through which said rotor passes, said permanent magnet of said rotor being magnetically coupled to said two polar expansions, said core having its first and second ends connected respectively to said two magnetic stator poles, this transducer being characterised in that said coil is situated in an opening, provided in said planar structure, the edge of which is closed on itself so that the part of said planar structure defining said second magnetic pole surrounds the part of this planar structure defining said first magnetic stator pole and said coil in projection in the general plane of said planar structure.
In particular, it is proposed to use the present invention for the manufacture of chronograph clockwork movements of small dimensions, in particular for xe2x80x9cladiesxe2x80x9d watches.